1. Field of the Invention
This invention relates generally to electronic and mechanical systems and methods for inspecting the interior of pipes and other conduits.
2. Description of the Related Art
There are many situations where it is desirable to internally inspect long lengths of pipe that are already in place, either underground, in a building, or underwater. For example, sewer and drain pipes frequently must be internally inspected to diagnose any existing problems and to determine if there are any breaks causing leakage or obstructions impairing the free flow of waste. It is also important to internally inspect steam pipes, heat exchanger pipes, water pipes, gas pipes, electrical conduits and fiber optic conduits for similar reasons. Frequently, pipes that are to be internally inspected have an internal diameter of six inches or less. It is sometimes necessary to inspect several hundred feet of pipe.
In the existing art, video pipe inspection systems may include a video camera that is forced down the pipe to display the pipe interior on a video display. The inspection is commonly recorded by means of a video recorder (VCR) or digital video disk (DVD). Conventional video pipe inspection systems may include a semi-rigid push cable that provides an electromechanical connection between a ruggedized camera head assembly enclosing and protecting the video camera and a rotatable push reel used to pay out cable and force the camera head assembly down the pipe. The video push cable must be specially designed to be flexible enough to make tight turns yet rigid enough to be pushed hundreds of feet down small diameter pipe and should also incorporate electrically conductive cable having the proper conductors and impedance for conveying the NTSC or other video signals to the video display unit and for coupling to external power and ground conductors. Examples of suitable video push cables are disclosed in U.S. Pat. No. 5,457,288 issued Oct. 10, 1995 to Mark S. Olsson and U.S. Pat. No. 5,808,239 issued Sep. 15, 1998 to Mark S. Olsson. A conventional video pipe inspection system may include a reel inside which the video push cable is wound for storage. The reel may be supported on a frame for rotation about a horizontal or a vertical axis for paying out the video push cable and for rewinding the video push cable for storage about the reel. This may require adding a slip ring assembly into the hub and/or axle of the reel to continue electrical connections between the proximal end of the video push cable and external circuits that power the video camera head assembly and receive video signals therefrom. The usual slip ring assembly is expensive and prone to failure. The frame and axle that rotatably support the reel also represent additional bulk and expense.
The video camera head assembly design and the manner in which it is connected to the distal end of the video push cable is critical to the performance and reliability of a video pipe inspection system. These structures must be rugged, yet the camera head assembly must be compact and its manner of connection to the video push cable flexible enough to bend through tight turns. It is also desirable to incorporate an electromagnetic transmitter near the video camera head assembly to provide a radiated signal from which the camera head position may be confirmed at a remote above-ground locator instrument. Heretofore the signals radiated from such transmitters have been inherently weak, making it difficult to precisely determine the underground position of the inspection assembly with a remote locator.
Existing systems known in the art provide the operator little more than direct video-image information, sometimes time-tagged by frame in recording. Most existing systems may provide a disoriented video image whenever the camera head assembly rotates away from alignment with the longitudinal axis of the pipe being inspected because of such issues as uncontrolled push cable torque or navigation through a bend or joint in the pipe. Video images from existing systems is provided with a single uniform (usually only moderate) resolution. Existing systems provide no means for tracking changes in camera orientation and distance traversed in the subject pipe or conduit nor to generate a map of the pipe from camera travel distances and headings.
Accordingly, there is an unmet need in the art for a pipe inspection system that can provide internal pipe images with accurate location and orientation information. Moreover, there is also a continuing need in the art for a pipe inspection system that can provide the location and orientation data required to provide an accurate mapping of the pipe under inspection to an operator. These unresolved problems and deficiencies are clearly felt in the art and are solved by this invention in the manner described below.